We propose to study HIV risk behaviors, seroprevalence, and possible HIV- induced mental changes in acute psychiatric inpatients, an understudied population targeted by the NIMH as a crucial area for HIV research. Our preliminary data indicate that 20% of our psychiatric inpatients are at high risk for HIV infection. Because many have not been tested, their seroprevalence is unknown; but our pilot data suggest at least an 8% rate of seropositivity among our inpatients. In addition, numerous case reports suggest that physically asymptomatic HIV seropositive individuals (HIV positive) may initially present with organic disorders that mimic functional psychiatric illnesses; however, whether clinically significant HIV-induced mental changes may occur prior to physical manifestations of immunosuppression remains controversial, yet important to study systematically despite the inherent difficulties. to address these issues, we will: 1) document self-reported HIV risk behaviors in 2,519 acute psychiatric inpatients aged 18-55, categorize these behaviors and correlate them with discharge diagnoses; 2) determine the seroprevalence of a subgroup (882) in an unlinked anonymous study using waste bloods; and 3) evaluate neuropsychiatrically 96 HIV positive to determine if their acute affective or psychotic disorders are HIV induced. This extensive evaluation will include standardized psychiatric, neurological, radiographic (MRI), immunological and neuropsychological assessments at entry and at 4 month intervals using for comparison 96 HIV- carefully matched for age, sex, education, risk behaviors, psychiatric diagnosis and dose-equivalent psychotropic medication. the knowledge obtained from this study will help identify the HIV counseling needs of specific psychiatric illnesses, document the impact of the AIDS epidemic on acute psychiatric inpatient services in a seroprevalent area, and guide the differential diagnosis of HIV-infected psychiatric inpatients.